Neuroscience
Abstract
Aberrant Tau inclusions in the locus coeruleus (LC) are the earliest detectable Alzheimer’s disease–like (AD-like) neuropathology in the human brain. However, why LC neurons are selectively vulnerable to developing early Tau pathology and degenerating later in disease and whether the LC might seed the stereotypical spread of Tau pathology to the rest of the brain remain unclear. Here, we show that 3,4-dihydroxyphenylglycolaldehyde, which is produced exclusively in noradrenergic neurons by monoamine oxidase A metabolism of norepinephrine, activated asparagine endopeptidase that cleaved Tau at residue N368 into aggregation- and propagation-prone forms, thus leading to LC degeneration and the spread of Tau pathology. Activation of asparagine endopeptidase–cleaved Tau aggregation in vitro and in intact cells was triggered by 3,4-dihydroxyphenylglycolaldehyde, resulting in LC neurotoxicity and propagation of pathology to the forebrain. Thus, our findings reveal that norepinephrine metabolism and Tau cleavage represent the specific molecular mechanism underlying the selective vulnerability of LC neurons in AD.
Authors
Seong Su Kang, Xia Liu, Eun Hee Ahn, Jie Xiang, Fredric P. Manfredsson, Xifei Yang, Hongbo R. Luo, L. Cameron Liles, David Weinshenker, Keqiang Ye
Abstract
Cancer cachexia is a major cause of patient morbidity and mortality, with no efficacious treatment or management strategy. Despite sharing pathophysiological features with a number of neuromuscular wasting conditions, including age-related sarcopenia, the mechanisms underlying cachexia remain poorly understood. Studies of related conditions suggest that pathological targeting of the neuromuscular junction (NMJ) may play a key role in cachexia, but this has yet to be investigated in human patients. Here, high-resolution morphological analyses were undertaken on NMJs of rectus abdominis obtained from patients undergoing upper GI cancer surgery compared with controls (N=30; n=1,165 NMJs). Cancer patients included those with cachexia and weight-stable disease. Despite the low skeletal muscle index and significant muscle fibre atrophy in patients with cachexia, NMJ morphology was fully conserved. No significant differences were observed in any of the pre- and post-synaptic variables measured. We conclude that NMJs remain structurally intact in rectus abdominis in both cancer and cachexia, suggesting that denervation of skeletal muscle is not a major driver of pathogenesis. The absence of NMJ pathology is in stark contrast to related conditions, such as age-related sarcopenia, and supports the hypothesis that intrinsic changes within skeletal muscle, independent of any changes in motor neurons, represent the primary locus of neuromuscular pathology in cancer cachexia.
Authors
Ines Boehm, Janice Miller, Thomas M. Wishart, Stephen J. Wigmore, Richard J.E. Skipworth, Ross A. Jones, Thomas H. Gillingwater
Abstract
Ventriculomegaly and hydrocephalus are associated with loss of function of glycine decarboxylase (Gldc) in mice and in humans suffering from Non-Ketotic Hyperglycinemia (NKH), a neurometabolic disorder characterised by accumulation of excess glycine. Here, we showed that ventriculomegaly in Gldc-deficient mice is preceded by stenosis of the Sylvian aqueduct and malformation or absence of the sub-commissural organ and pineal gland. Gldc functions in the glycine cleavage system, a mitochondrial component of folate metabolism, whose malfunction results in accumulation of glycine and diminished supply of glycine-derived one-carbon units to the folate cycle. We showed that inadequate one-carbon supply, as opposed to excess glycine is the cause of hydrocephalus associated with loss of function of the glycine cleavage system. Maternal supplementation with formate prevented both ventriculomegaly, as assessed at pre-natal stages, and post-natal development of hydrocephalus in Gldc-deficient mice. Furthermore, ventriculomegaly was rescued by genetic ablation of 5,10-methylene tetrahydrofolate reductase (Mthfr), which results in retention of one-carbon groups in the folate cycle at the expense of transfer to the methylation cycle. In conclusion, a defect in folate metabolism can lead to pre-natal aqueduct stenosis and resultant hydrocephalus. These defects are preventable by maternal supplementation with formate, which acts as a one-carbon donor.
Authors
Chloe Santos, Yun Jin Pai, M. Raasib Mahmood, Kit-Yi Leung, Dawn Savery, Simon N. Waddington, Andrew J. Copp, Nicholas D.E. Greene
Lysine acetyltransferase 8 is involved in cerebral development and syndromic intellectual disability
Abstract
Epigenetic integrity is critical for many eukaryotic cellular processes. An important question is how different epigenetic regulators control development and impact disease. Lysine acetyltransferase 8 (KAT8) is critical for acetylation of histone H4 at lysine 16 (H4K16), an evolutionarily conserved epigenetic mark. It is unclear what roles KAT8 plays in cerebral development and human disease. Here, we report that cerebrum-specific knockout mice displayed cerebral hypoplasia in the neocortex and hippocampus, along with improper neural stem and progenitor cell (NSPC) development. Mutant cerebrocortical neuroepithelia exhibited faulty proliferation, aberrant neurogenesis, massive apoptosis and scant H4K16 propionylation. Mutant NSPCs formed poor neurospheres, and pharmacological KAT8 inhibition abolished neurosphere formation. Moreover, we describe KAT8 variants in nine patients with intellectual disability, seizures, autism, dysmorphisms and other anomalies. The variants altered chromobarrel and catalytic domains of KAT8, thereby impairing nucleosomal H4K16 acetylation. Valproate was effective for treating epilepsy in at least two of the individuals. This study uncovers a critical role of KAT8 in cerebral and NSPC development, identifies nine individuals with KAT8 variants, and links deficient H4K16 acylation directly to intellectual disability, epilepsy and other developmental anomalies.
Authors
Lin Li, Mohammad Ghorbani, Monika Weisz-Hubshman, Justine Rousseau, Isabelle Thiffault, Rhonda E. Schnur, Catherine Breen, Renske Oegema, Marjan M.M. Weiss, Quinten Waisfisz, Sara Welner, Helen Kingston, Jordan A. Hills, Elles M.J. Boon, Lina Basel-Salmon, Osnat Konen, Hadassa Goldberg-Stern, Lily Bazak, Shay Tzur, Jianliang Jin, Xiuli Bi, Michael Bruccoleri, Kirsty McWalter, Megan T. Cho, Maria Scarano, G. Bradley Schaefer, Susan S. Brooks, Susan Starling Hughes, K.L.I. van Gassen, Johanna M. van Hagen, Tej K. Pandita, Pankaj B. Agrawal, Philippe M. Campeau, Xiang-Jiao Yang
Abstract
A single sub-anesthetic dose of ketamine, an NMDA receptor (NMDAR) antagonist, produces rapid and sustained antidepressant actions in depressed patients, addressing a major unmet need for the treatment of mood disorders. Ketamine produces a rapid increase in extracellular glutamate and synaptic formation in the prefrontal cortex, but the initial cellular trigger that initiates these and its behavioral actions has not been identified. To address this question, we used a combination of viral shRNA and conditional mutation to produce cell specific knockdown or deletion of a key NMDAR subunit, GluN2B, implicated in the actions of ketamine. The results demonstrate that the antidepressant actions of ketamine were blocked by GluN2B-NMDAR knockdown on GABA (Gad1) interneurons, as well as subtypes expressing somatostatin (Sst), or parvalbumin (Pvalb), but not glutamate principle neurons in the mPFC. Further analysis of GABA subtypes showed that cell specific knockdown or deletion of GluN2B in Sst interneurons blocked or occluded the antidepressant actions of ketamine and revealed sex-specific differences that are associated with excitatory postsynaptic currents on mPFC principle neurons. These findings demonstrate that GluN2B-NMDARs on GABA interneurons are the initial cellular trigger for the rapid antidepressant actions of ketamine and show sex-specific adaptive mechanisms to GluN2B modulation.
Authors
Danielle M. Gerhard, Santosh Pothula, Rong-Jian Liu, Min Wu, Xiao-Yuan Li, Matthew J. Girgenti, Seth R. Taylor, Catharine H. Duman, Eric Delpire, Marina Picciotto, Eric S. Wohleb, Ronald S. Duman
Abstract
Neuronal hyperexcitability and cytoplasmic mislocalization of the nuclear RNA binding proteinTDP43 are universal features in amyotrophic lateral sclerosis (ALS), but the relationship between these phenomena remains poorly defined. Here, we show that neuronal hyperexcitability drives TDP43 pathology by upregulating shortened (s)TDP43 splice variants missing the canonical C-terminus. sTDP43 isoforms preferentially accumulate in the cytoplasm,forming insoluble inclusions that sequester full-length TDP43 via preserved N-terminal interactions. Consistent with these findings, sTDP43 overexpression is highly toxic to mammalian neurons, suggesting that neurodegeneration results from complementary gain- and loss-of-function mechanisms. In humans and mice, sTDP43 transcripts are significantly enriched in vulnerable motor neurons, and we observed a striking accumulation of sTDP43 protein within neurons and glia of ALS patients. These studies uncover a hitherto unknown role of alternative TDP43 splice isoforms in ALS, and indicate that sTDP43 production may be a key contributor to the susceptibility of motor neurons in ALS.
Authors
Kaitlin Weskamp, Elizabeth M. Tank, Roberto Miguez, Jonathon P. McBride, Nicolás B. Gómez, Matthew White, Ziqiang Lin, Carmen Moreno Gonzalez, Andrea Serio, Jemeen Sreedharan, Sami J. Barmada
Abstract
Parkinson's disease (PD) is a neurodegenerative disorder associated with loss of striatal dopamine, secondary to degeneration of midbrain dopamine (mDA) neurons in the substantia nigra, rendering cell transplantation a promising therapeutic strategy. To establish human induced pluripotent stem cell (hiPSC)-based autologous cell therapy, we report a platform of core techniques for the production of mDA progenitors as a safe and effective therapeutic product. First, by combining metabolism-regulating microRNAs with reprogramming factors, we developed a method to more efficiently generate clinical grade iPSCs, as evidenced by genomic integrity and unbiased pluripotent potential. Second, we established a “spotting”-based in vitro differentiation methodology to generate functional and healthy mDA cells in a scalable manner. Third, we developed a chemical method that safely eliminates undifferentiated cells from the final product. Dopaminergic cells thus produced express high levels of characteristic mDA markers, produce and secrete dopamine, and exhibit electrophysiological features typical of mDA cells. Transplantation of these cells into rodent models of PD robustly restores motor dysfunction and reinnervates host brain, while showing no evidence of tumor formation or redistribution of the implanted cells. We propose that this platform is suitable for the successful implementation of human personalized autologous cell therapy for PD.
Authors
Bin Song, Young Cha, Sanghyeok Ko, Jeha Jeon, Nayeon Lee, Hyemyung Seo, Kyung-joon Park, In-Hee Lee, Claudia Lopes, Melissa Feitosa, María José Luna, Jin Hyuk Jung, Jisun Kim, Dabin Hwang, Bruce Cohen, Martin Teicher, Pierre Leblanc, Bob Carter, Jeffrey H. Kordower, Vadim Y. Bolshakov, Sek Won Kong, Jeffrey S. Schweitzer, Kwang-Soo Kim
Abstract
Leptomeningeal anastomoses or pial collateral vessels play a critical role in cerebral blood flow (CBF) restoration following ischemic stroke. The magnitude of this adaptive response is postulated to be controlled by the endothelium, although the underlying molecular mechanisms remain under investigation. Here we demonstrated that endothelial genetic deletion, using EphA4f/f/Tie2-Cre and EphA4f/f/VeCahderin-CreERT2 mice and vessel painting strategies, implicated EphA4 receptor tyrosine kinase as a major suppressor of pial collateral remodeling, CBF and functional recovery following permanent middle cerebral artery occlusion. Pial collateral remodeling is limited by the cross talk between EphA4-Tie2 signaling in vascular endothelial cells, which is mediated through p-Akt regulation. Furthermore, peptide inhibition of EphA4 resulted in acceleration of the pial arteriogenic response. Our findings demonstrate EphA4 is a negative regulator of Tie2 receptor signaling which limits pial collateral arteriogenesis following cerebrovascular occlusion. Therapeutic targeting of EphA4 and/or Tie2 represents an attractive new strategy for improving collateral function, neural tissue health and functional recovery following ischemic stroke.
Authors
Benjamin Okyere, William A. Mills III, Xia Wang, Michael Chen, Jiang Chen, Amanda Hazy, Yun Qian, John B. Matson, Michelle H. Theus
Abstract
While the impact of T helper 17 (Th17) cells in autoimmunity is undisputable, their pathogenic effector mechanism is still enigmatic. We have discovered SNARE complex proteins in Th17 cells enabling a vesicular glutamate release pathway inducing local intracytoplasmic calcium release and subsequent damage in neurons. This pathway is glutamine dependent and triggered by binding of β1-integrin to VCAM-1 on neurons in inflammatory context. Glutamate secretion could be blocked by inhibiting either glutaminase or KV1.3 channels, known to be linked to integrin expression and highly expressed on stimulated T cells. While KV1.3 is not expressed in the CNS tissue, intrathecal administration of a KV1.3 channel blocker or a glutaminase inhibitor ameliorated disability in experimental neuroinflammation. In humans, T cells from multiple sclerosis patients secreted higher levels of glutamate, and cerebrospinal fluid glutamine levels were increased. Altogether, our findings demonstrate that β1-integrin- and KV1.3 channel-dependent signaling stimulates glutamate release from Th17 cells upon direct cell-cell contact between Th17 cells and neurons.
Authors
Katharina Birkner, Beatrice Wasser, Tobias Ruck, Carine Thalman, Dirk Luchtman, Katrin Pape, Samantha Schmaul, Lynn Bitar, Eva-Maria Krämer-Albers, Albrecht Stroh, Sven G. Meuth, Frauke Zipp, Stefan Bittner
Abstract
BACKGROUND Spinal muscular atrophy (SMA) is caused by deficient expression of survival motor neuron (SMN) protein. New SMN-enhancing therapeutics are associated with variable clinical benefits. Limited knowledge of baseline and drug-induced SMN levels in disease-relevant tissues hinders efforts to optimize these treatments.METHODS SMN mRNA and protein levels were quantified in human tissues isolated during expedited autopsies.RESULTS SMN protein expression varied broadly among prenatal control spinal cord samples, but was restricted at relatively low levels in controls and SMA patients after 3 months of life. A 2.3-fold perinatal decrease in median SMN protein levels was not paralleled by comparable changes in SMN mRNA. In tissues isolated from nusinersen-treated SMA patients, antisense oligonucleotide (ASO) concentration and full-length (exon 7 including) SMN2 (SMN2-FL) mRNA level increases were highest in lumbar and thoracic spinal cord. An increased number of cells showed SMN immunolabeling in spinal cord of treated patients, but was not associated with an increase in whole-tissue SMN protein levels.CONCLUSIONS A normally occurring perinatal decrease in whole-tissue SMN protein levels supports efforts to initiate SMN-inducing therapies as soon after birth as possible. Limited ASO distribution to rostral spinal and brain regions in some patients likely limits clinical response of motor units in these regions for those patients. These results have important implications for optimizing treatment of SMA patients and warrant further investigations to enhance bioavailability of intrathecally administered ASOs.FUNDING SMA Foundation, SMART, NIH (R01-NS09677, R01-NS062269), Ionis Pharmaceuticals, and PTC Therapeutics. Biogen provided support for absolute real-time RT-PCR.
Authors
Daniel M. Ramos, Constantin d’Ydewalle, Vijayalakshmi Gabbeta, Amal Dakka, Stephanie K. Klein, Daniel A. Norris, John Matson, Shannon J. Taylor, Phillip G. Zaworski, Thomas W. Prior, Pamela J. Snyder, David Valdivia, Christine L. Hatem, Ian Waters, Nikhil Gupte, Kathryn J. Swoboda, Frank Rigo, C. Frank Bennett, Nikolai Naryshkin, Sergey Paushkin, Thomas O. Crawford, Charlotte J. Sumner
Copyright © 2020 American Society for Clinical Investigation
ISSN: 0021-9738 (print), 1558-8238 (online)